The present invention relates to transition metal complexes of the formula (Ia) or (Ib), 
where the substituents and indices have the following meanings:
R1 to R3 are hydrogen, C1-C10-alkyl, 5- to 7-membered cycloalkyl, which in turn may be substituted by C1-C10-alkyl, are C6-C15-aryl or arylalkyl, where the radicals together with adjacent radicals in each case with the linking atoms may form a saturated or unsaturated ring having 5 to 15 carbon atoms, or are Si(R4)3 where
R4 is C1-C10-alkyl, C3-C10-cycloalkyl or C6-C15-aryl,
M is titanium, zirconium, hafnium, vanadium, niobium or tantalum or an element of the IIIrd subgroup of the Periodic Table or of the lanthanoids,
x is fluorine, chlorine, bromine, iodine, hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl having 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, xe2x80x94OR5 or xe2x80x94NR5R6,
n is 1, 2 or 3, where n is the valency of M minus the number 2,
xe2x80x83where
R5 and R6 are C1-C10-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl having in each case 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical and
the radicals X are identical or different,
Y is 
xe2x80x83where
R7 is C1-C10-alkyl, C6-C15-aryl, C3-C10-cycloalkyl or C7-C18-alkylaryl or is C1-C10-alkyl, C6-C15-aryl, C3-C10-cycloalkyl or C7-C18-alkylaryl, each of which is mono- or polysubstituted by Si(R8)3, SR8, 
xe2x80x83OSi(R8)3, N(R8)2, P(R8)2 or a combination thereof, or is Si(R8)3 where
nxe2x80x2 and mxe2x80x2 are each 1, 2, 3 or 4 and
R8 is hydrogen, C1-C10-alkyl, C6-C15-aryl, which may in turn be substituted by C1-C4-alkyl groups, or is C3-C10-cycloalkyl,
where the radicals R8 are identical or different,
Z is a three-way bridge and
A and A1 are two-way bridges.
Additionally, the invention relates to processes for preparing the transition metal complexes, to compounds which are employed as intermediates for their preparation, to the use of the transition metal complexes for polymerizing olefins, to processes for polymerizing olefins, to homo- or copolymers of ethylene or of propylene with other C2-C12-alk-1-enes, to their use for preparing films, fibers or moldings, and to the films, fibers or moldings made from these polymers.
Recently, metallocene catalysts have been used increasingly for polymerizing or copolymerizing ethylene or propylene. In the case of ethylene polymerization, it is frequently desirable to obtain a high content of comonomers such as but-1-ene, hex-1-ene or oct-1-ene in the ethylene copolymers. In the case of propylene polymerization, it is usually attempted to achieve an isotactic structure of the polymer chains. Using metallocene catalysts, these properties can be controlled via the ligand structure.
It is generally assumed that the opening angle between the cyclopentadienyl rings of the metallocene has great influence on the incorporation behavior. A large opening angle can be achieved, for example, by bridging the rings with an SiMe2- or C2H4-bridge. Such metallocene catalysts are described, for example, in EP-A 336 128. Because of the bridging, these complexes can exist both in racemic and in meso form. The racemic metallocenes are particularly suitable for use in propylene polymerization, since stereoselective catalysts are required here. However, it is a disadvantage of these metallocenes that usually a mixture of racemic and meso form is obtained in the synthesis, from which the meso form has to be removed at high expense.
In other metallocene catalysts, a cyclopentadienyl ring is replaced by a heteroligand, for example an amide group. In these metallocenes, the amide group is linked covalently via a bridge (for example SiMe2) with the ring system. Compounds of this type are described, for example, in EP-A 416 815 and EP-A 420 436. It is known that metallocene complexes of this type are particularly suitable for incorporating comonomers in the ethylene/xcex1-olefin copolymerization and give a high molar mass. However, it has hitherto not been possible to obtain isotactic polypropylene with complexes of this type, since the metal center did not have C2 symmetry. The resulting polypropylene was atactic with partially syndiotactic portions (WO 94/00500, U.S. Pat. No. 5,096,867, EP-A 520 732, U.S. Pat. No. 5 504 169).
Beside metallocenes having a cyclopentadienyl ring and a heteroatom as ligands, there are also known more complex systems, for example having a fluorenyl system and a heteroatom (Okuda et al., Organometallics 1995, 14, 789-795). However, the chiral metal atom is likewise not obtained. While U.S. Pat. No. 5,026,798 describes the synthesis of partially isotactic polypropylene using catalysts of this type, more recent investigations (A. L. McKnight et al. Organometallics 1997, 16, 2879-2885) show that identical systems achieve only isotacticities which are in the range of what was statistically expected. Thus, the ligand skeleton employed has no influence on the isotacticity.
It is an object of the present invention to remedy the disadvantages described above and to develop a metallocene complex which offers technical advantages in the polymerization of ethylene and shows, in particular, high incorporation of comonomers and affords a high molar mass. Furthermore, the metallocene should be capable of catalyzing the preparation of isotactic polypropylene, where it should likewise afford a high molar mass. Finally, the structure of the metallocene should be such that it can be prepared in a technically simple manner and that, in particular, a meso form which, for many applications, would have to be removed at great expense, can not be generated in the synthesis.
We have found that this object is achieved by the transition metal complexes defined at the outset. Furthermore, we have found processes for their preparation, compounds which are employed as intermediates for their preparation, the use of the transition metal complexes for polymerizing olefins, processes for polymerizing olefins, homo- or copolymers of ethylene or of propylene with other C2-C12-alk-1-enes, their use for preparing films, fibers or moldings, and the films, fibers or moldings made from these polymers.
The substituents R1 to R3 are preferably a hydrogen atom, a C1-C6-alkyl radical, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, and also the various isomers of pentyl or hexyl, or an aryl radical, such as phenyl or naphthyl, which may be unsubstituted or substituted by alkyl radicals of the group just mentioned. Preference is likewise given to substituents R1 to R3, which form, with adjacent substituents R1 to R3 or with substituents of the bridge A1, in each case with the linking atoms, a saturated or unsaturated ring having 5 to 10 carbon atoms.
Among the transition metals M in the formulae (Ia) and (Ib), preference is given to the elements of the 4th subgroup of the Periodic Table, i.e. titanium, zirconium and hafnium. Particular preference is given to titanium and zirconium.
Suitable ligands X are in particular the halogens, fluorine, chlorine, bromine and iodine, and particular preference is given to chlorine. Among the C1-C10-alkyl radicals, methyl, ethyl, propyl and butyl are particularly preferred. The preferred C6-C15-aryl radical is the phenyl radical.
The number n corresponds to the valency of M minus the number 2, i.e. for the complexes of titanium, zirconium or hafnium, n=2, for the complexes of vanadium, niobium or tantalum, n=3, and for the elements of the 3rd subgroup of the Periodic Table, i.e. scandium, yttrium and lanthanum, and of the lanthanoids, n=1.
Among the heteroligands Y, preference is given to xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94 and 
and substituents at the nitrogen atom which may be particularly mentioned are methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, cyclohexyl, phenyl, benzyl and Si(R8)3. Preferred substituents at the nitrogen atom also include radicals R7 which are mono- or polysubstituted by groups acting as Lewis bases, such as si(R8)3, SR8, OR8, 
OSi(R8)3, N(R8)2, P(R8)2 or combinations of these groups, where nxe2x80x2 and mxe2x80x2 are in each case the numbers 1, 2, 3 or 4. Particularly preferred groups here are OR8 and N(R8)2. Particularly preferred substituted radicals R7 are substituted C1-C10-alkyl groups, in particular substituted methyl groups, ethyl groups, n-propyl groups, isopropyl groups, n-butyl groups, tert-butyl groups and cyclohexyl groups.
The bridge Z is usually a three-way organic or organometallic atom group which is attached, both directly and via the bridges A and A1, to the cyclopentadienyl ring system and to the heteroligand Y.
Suitable bridges Z are, for example, 
where
R9 to R12 are each hydrogen atom, a halogen atom, a C1-C10-alkyl group, a C1-C10-fluoroalkyl group, a C6-C10-fluoroaryl group, a C6-C10-aryl group, a C1-C10-alkoxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C8-C40-arylalkenyl group or a C7-C40-alkylaryl group or two radicals R9 to R12 together with the linking atoms, form a saturated or unsaturated ring having 4 to 15 carbon atoms, and
M1 is silicon, germanium or tin.
Suitable bridges Z are, in particular, the radicals 
in which
R9 to R11 are methyl, ethyl, tert-butyl or phenyl. The bridge z is particularly preferably Si(Me), Si(Ph), Si(t-Bu) or C(CH3)2C(CH3).
The two-way bridges A and A1 effect a second link of the bridge Z to the cyclopentadienyl ring system. Thus, the xe2x80x9crightxe2x80x9d and the xe2x80x9cleftxe2x80x9d side of the metallocene complex differ, and generation of a stereoselective polymerization center is possible.
The bridge A may for its part consist of several two-way bridges A2, and A is preferably xe2x80x94(A2)mxe2x80x94 where m is from 1 to 6. Particularly preferably, the bridge A comprises from 1 to 3 A2 members and in particular 2 A2 members.
In general, the A1 or A2 members are organic or organometallic atom groups which preferably consist either of a substituted bridge atom or of a substituted or unsubstituted aromatic ring. A1 and A2 are, for example, 
where A1 and the individual members A2 of A are identical or different, and
R13 to R16 are identical or different and are each a hydrogen atom, a halogen atom, a C1-C10-alkyl group, a C1-C10-fluoroalkyl group, a C6-C10-fluoroaryl group, a C6-C10-aryl group, a C1-C10-alkoxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C8-C40-arylalkenyl group or a C7-C40-alkylaryl group, or where two adjacent radicals in each case with the linking atoms form a saturated or unsaturated ring having 5 to 15 carbon atoms, or
where a radical R13 to R16 of A1 together with an adjacent radical R2 or R3 form a saturated or unsaturated ring system which has 5 to 15 carbon atoms, including the linking atoms.
The members A1 or A2 preferably contain the bridge atoms carbon, silicon, nitrogen or oxygen. Preferred substituents at the bridge atoms are hydrogen, methyl, ethyl and phenyl. Preference is also given to phenyl rings which may carry, as preferred substituents, methyl, ethyl or phenyl groups.
Particular preference is given to transition metal complexes of the formula (Ia) or (Ib) in which the group A1 together with an adjacent radical R2 or R3 forms a saturated or unsaturated ring. Very particular preference is given here to transition metal complexes of the formula (Iaxe2x80x2), 
in which the groups A1 and R3 of the formula (Ia) together form an unsaturated ring having 6 carbon atoms and
R17 to R19 are each a hydrogen atom, a C1-C10-alkyl group, a 5- to 7-membered cycloalkyl group, which may in turn be substituted by C1-C10-alkyl, are a C6-C15-aryl group or an arylalkyl group, or where two adjacent radicals in each case with the linking atoms form a saturated or unsaturated ring having 5 to 15 carbon atoms, or are Si(R4)3.
The substituents R17 to R19 are preferably a hydrogen atom, a C1-C6-alkyl radical, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl, and the various isomers of pentyl or hexyl, or an aryl radical, such as phenyl or naphthyl, which may be unsubstituted or substituted by alkyl radicals from the group just mentioned. Preference is also given to adjacent substituents R17 to R19 which, in each case with the linking atoms, form a saturated or unsaturated ring having 5 to 10 carbon atoms.
The transition metal complexes according to the invention can be present as such. However, it is also possible that, in addition to the ligands X, Y and the cyclopentadienyl ring system, 1 to 3 neutral Lewis bases, such as tetrahydrofuran, diethyl ether, trimethylamine or N,N-dimethylaniline, are coordinated to the transition metal atom. It is also possible that the transition metal complexes are present as dimers.
For preparing the transition metal complexes according to the invention, a process has been found which comprises reacting cyclopentadiene compounds of the formula (IIa) or (IIb), 
in which
R1 to R3 and A1 are each as defined above and
X1 is hydrogen or a halogen and
X2 is hydrogen or a radical of the formula M2R20(o-1)in which
M2 is an element of the 1st-4th main group of the Periodic Table,
R20 is a halogen, a C1-C10-alkyl group, a 5- to 7-membered cycloalkyl group, which may in turn be substituted by C1-C10-alkyl, is a C6-C15-aryl group or an arylalkyl group, where the radicals R20 may be identical or different, and
o is the valency of M2,
with compounds of the formula (III) 
in which
Z and A are each as defined above,
X3 and X4 are each a halogen and
X5 is hydrogen, a halogen or a group 
xe2x80x83where
R21 and R22 are each hydrogen, C1-C10-alkyl, C3-C10-cycloalkyl or C6-C15-aryl,
to give compounds of the formula (IVa) or (Ivb), 
preparing from these by intramolecular ring closure the compounds of the formula (Va) or (Vb), 
which are converted into compounds of the formula (VIa) or (VIb), 
in which
X6 is hydrogen or a radical of the formula M3R23(p-1), in which,
M3 is an element of the 1st-4th main group of the Periodic Table,
R23 is a halogen, a C1-C10-alkyl group, a 5- to 7-membered cycloalkyl group, which may in turn be substituted by C1-C10-alkyl, is a C6-C15-aryl group or an arylalkyl group, where the radicals R23 may be identical or different, and
p is the valency of M3,
which are then converted into the transition metal complexes of the formula (Ia) or (Ib).
A preferred process for preparing the transition metal complexes according to the invention comprises reacting indene compounds of the formula (IIaxe2x80x2) 
in which X1, X2, R1, R2 and R17 to R19 are each as defined above, with a compound of the formula (III) to give compounds of the formula (IVaxe2x80x2), 
in which X3, X5, Z and A are each as defined above,
from which, by intramolecular ring closure, the compounds of the general formula (Vaxe2x80x2) are prepared, 
which are reacted to give compounds of the formula (VIaxe2x80x2) 
in which X6 and Y are each as defined above,
which are then converted into the transition metal complexes of the formula (Iaxe2x80x2).
The starting materials (IIa), (IIaxe2x80x2) and (IIb) and also (III) are known or can be prepared in a known manner. Some of them are commercially available.
They can be reacted by the customary methods of substitution on cyclopentadiene systems, generally in solvents, where preference is given to using ethereal solvents, such as diethyl ether or THF. The addition sequence per se is immaterial. Preference is given to initially charging the compounds (IIa), (IIaxe2x80x2) or (IIb) in the solvent and to adding the compound or the compounds (III) neat or in solution. This can be carried out at from xe2x88x92100 to +100xc2x0 C., preferably from xe2x88x9280 to +30xc2x0 C. The products (Iva), (Ivaxe2x80x2) or (IVb) can then be obtained, for example, by extraction (in the case of one or more other solid reaction products) or by distillation (in the case of one or more other liquid reaction products).
The intramolecular ring closure to the compounds (Va), (Vaxe2x80x2) or (Vb) can generally be carried out by the known methods of Cxe2x80x94C, C-heteroatom or heteroatom-heteroatom bond formation, as described, for example, in Jerry March, Advanced Organic Chemistry, John Wiley and Sons, New York 1985 or Organikum, VEB Deutscher Verlag der Wissenschaften, Berlin 1977. Depending on the nature of the radicals A1, X1, A and X5, particularly suitable reactions which may be mentioned are Friedel-Crafts alkylation, Friedel-Crafts acylation, azo coupling, radical bond formation, Wurz reaction, addition of a heteroatom-hydrogen bond to a Cxe2x80x94C, C-heteroatom or heteroatom-heteroatom multiple bond (for example hydrosilylation, hydroboration, hydroamination), formation of Schiff bases, formation of amides, esterification (also organometal-catalyzed), etherification, Grignard reaction, McMurry coupling, Diels-Alder reaction, cross-coupling of aromatics, Heck reaction, Suzuki coupling, Reformatsky reaction, Wittig reaction, Ritter reaction and condensation reactions (for example aldol condensation, Knoevenagel condensation, Perkin reaction). In the case of compounds of the formula (IVaxe2x80x2), particular preference is given to the reactions Friedel-crafts alkylation or Friedel-Crafts acylation. The Friedel-Crafts alkylation can also be carried out as a two-step synthesis, starting from the unsaturated compound and the in situ formation of the appropriately halogenated precursor.
The compounds (Va), (Vaxe2x80x2) or (Vb) are subsequently reacted with compounds of the formula YX6X7 in which
Y is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, 
xe2x80x83where,
R7 is C1-C10-alkyl, C6-C15-aryl, C3-C10-cycloalkyl or C7-C18-alkylaryl or is C1-C10-alkyl, C6-C15-aryl, C3-C10-cycloalkyl or C7-C18-alkylaryl, each of which is mono- or polysubstituted by Si(R8)3 SR8, OR8, 
xe2x80x83OSi(R8)3, N(R8)2, P(R8)2 or a combination thereof, or is Si(R8)3 where
nxe2x80x2 and mxe2x80x2 are each 1, 2, 3 or 4 and
R8 is hydrogen, C1-C10-alkyl, C6-C15-aryl, which may in turn be substituted by C1-C4-alkyl groups, or is C3-C10-cycloalkyl,
where the radicals R8 are identical or different, and
X6 and X7 is hydrogen or a radical of the formula M3R23(p-1), in which,
M3 is an element of the 1st-4th main group of the Periodic Table,
R23 is a halogen, a C1-C10-alkyl group, a 5- to 7-membered cycloalkyl group, which may in turn be substituted by C1-C10-alkyl, is a C6-C15-aryl group or an arylalkyl group, where the radicals R23 may be identical or different, and
p is the valency of M3.
By reacting YX6X7 with the radical X3, an equivalent of a compound of the formula X7X3 is cleaved off with formation of the bond between Z and Y. Preferred compounds of the formula YX6X7 are monosubstituted amines and alcohols or their organometal derivatives, and particular preference is given to methylamine, ethylamine, tert-butylamine and phenylamine. If an acid is liberated during the reaction (i.e. X7 is a hydrogen), a base is usually added to the reaction mixture.
The reaction is generally carried out in solution, and preference is given to using ethereal solvents, such as diethyl ether or THF. The addition sequence per se is immaterial. Preference is given to initially charging the compound (Va), (Vaxe2x80x2) or (Vb) in the solvent and to adding the compound YX6X7 neat, in solution or in the form of a hydrosalt (for example a hydrochloride) which is then converted into the corresponding base using a strong base. This can be carried out at from xe2x88x92100 to +100xc2x0 C., preferably from xe2x88x9280 to +70xc2x0 C. When amines are employed, it has been found to be advantageous to employ an excess of double the amount of amine, since it acts in this case simultaneously as base.
The resulting compounds (VIa), (VIaxe2x80x2) or (VIb) can be converted by known methods into the corresponding metal complexes. The complexation methods are described, for example, in EP-A 416 815, EP-A 420 436 or Okuda et al., Organometallics 14, (1995), 789-795. Preference is given to using the compounds (VIa), (VIaxe2x80x2) or (VIb) where X6=Li. The reaction can be carried out, for example, using tetrasubstituted Tixe2x80x94, Zrxe2x80x94 or Hf compounds. Preferred metals are titanium and zirconium. Preferred substituents are halogens, in particular chlorine. The tetrahalides can also be employed in the form of base adducts (for example with THF).
The reaction is generally carried out in solution, and preference is given to using ethereal solvents, such as diethyl ether or THF. The addition sequence per se is immaterial. Preference is given to initially charging the compounds (VIa), (VIaxe2x80x2) or (VIb) in the solvent and adding the metal compound neat or in solution. This can be carried out at temperatures of from xe2x88x92100 to +100xc2x0 C., preferably from xe2x88x9280 to +30xc2x0 C.
The transition metal complexes (Ia), (Iaxe2x80x2) and (Ib) according to the invention have an asymmetric arrangement of the ligands at the metal atom. Owing to this structure, the transition metal complexes (Ia), (Iaxe2x80x2) and (Ib) can not be present in a meso form. However, as a result of the unsymmetric substitution at the cyclopentadienyl ligand, the polymerization proceeds stereoselectively.
The present invention furthermore relates to the intermediates, employed for preparing the transition metal complexes (Iaxe2x80x2) according to the invention, of the formula (VIaxe2x80x2) 
in which the substituents and indices have the following meanings:
R1, R2 and R17 to R19 are hydrogen, C1-C10-alkyl, 5- to 7-membered cycloalkyl, which in turn may be substituted by C1-C10-alkyl, are C6-C15-aryl or arylalkyl, where two adjacent radicals, in each case with the linking atoms, may form a saturated or unsaturated ring having 5 to 15 carbon atoms, or are si(R4)3 where
R4 is C1-C10-alkyl, C3-C10-cycloalkyl or C6-C15-aryl,
X6 is hydrogen or a radical of the formula M3R23(p-l), in which
M3 is an element of the 1st-4th main group of the Periodic Table,
R23 is a halogen, a C1-C10-alkyl group, a 5- to 7-membered cycloalkyl group, which in turn may be substituted by C1-C10-alkyl, is a C6-C15-aryl group or an arylalkyl group, where the radicals R23 may be identical or different, and
P is the valency of M3,
Y is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, 
xe2x80x83where
R7 is C1-C10-alkyl, C6-C15-aryl, C3-C10-cycloalkyl or C7-C18 -alkylaryl or is C1-C10-alkyl, C6-C15-aryl, C3-C10-cycloalkyl or C7-C18-alkylaryl, each of which is mono- or polysubstituted by Si(R8)3, SR8, OR8, 
xe2x80x83OSi(R8)3, N(R8)2, P(R8)2 or a combination thereof, or is Si(R8)3 where
nxe2x80x2 and mxe2x80x2 are each 1, 2, 3 or 4 and
R8 is hydrogen, C1-C10-alkyl, C6-C15-aryl, which may in turn be substituted by C1-C4-alkyl groups, or is C3-C10-cycloalkyl,
where the radicals R8 are identical or different, 
where
R9 to R12 are each a hydrogen atom, a halogen atom, a C1-C10-alkyl group, a C1-C10-fluoroalkyl group, a C6-C10-fluoroaryl group, a C6-C10-aryl group, a C1-C10-alkoxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C8-C40-arylalkenyl group or a C7-C40-alkylaryl group, or where two adjacent radicals, in each case with the linking atoms, form a saturated or unsaturated ring having 4 to 15 carbon atoms, and,
M1 is silicon, germanium or tin, and
A is a bridge xe2x80x94(A2)mxe2x80x94 where
m is from 1 to 6, and 
where the individual members A2 of A are identical or different.
The present invention furthermore also relates to the intermediates, employed for preparing the transition metal complexes Iaxe2x80x2 according to the invention, of the formula (IVaxe2x80x2) 
in which the substituents and indices have the following meanings:
R1, R2 and R17 to R19 are hydrogen, C1-C10-alkyl, 5- to 7-membered cycloalkyl, which in turn may be substituted by C1-C10-alkyl, C6-C15-aryl or arylalkyl, where two adjacent radicals, in each case with the linking atoms, may form a saturated or unsaturated ring having 5 to 15 carbon atoms, or are Si(R4)3 where
R4 is C1-C10-alkyl, C3-C10-cycloalkyl or C6-C15-aryl,
X1 is hydrogen or a halogen,
X3 is a halogen and
X5 is hydrogen, a halogen or a group 
xe2x80x83where
R21 and R22 are each hydrogen, C1-C10-alkyl, C3-C10-cycloalkyl or C6-C15-aryl, 
where
R9 to R12 are each a hydrogen atom, a halogen atom, a C1-C10-alkyl group, a C1-C10-fluoroalkyl group, a C6-C10-fluoroaryl group, a C6-C10-aryl group, a C1-C10-alkoxy group, a C2-C10-alkenyl group, a C7-C40-arylalkyl group, a C8-C40-arylalkenyl group or a C7-C40-alkylaryl group, or where two adjacent radicals, in each case with the linking atoms, form a saturated or unsaturated ring having 4 to 15 carbon atoms, and
M1 is silicon, germanium or tin, and
A is a bridge xe2x80x94(A2)mxe2x80x94 where
m is from 1 to 6, and 
where the individual members A2 of A are identical or different.
The transition metal complexes according to the invention are suitable, for example, for polymerizing olefins and in particular for polymerizing xcex1-olefins, i.e. hydrocarbons having terminal double bonds. Suitable monomers can be functionalized olefinically unsaturated compounds, such as ester or amide derivatives of acrylic or methacrylic acid, for example acrylates, methacrylates or acrylonitrile. Preference is given to non-polar olefinic compounds, including aryl-substituted xcex1-olefins such as styrene. Particularly preferred xcex1-olefins are linear or branched C2-C12-alk-1-enes, in particular linear C2-C10-alk-1-enes, such as ethylene, propylene, but-1-ene, pent-1-ene, hex-1-ene, hept-1-ene, oct-1-ene, non-1-ene, dec-1-ene or 4-methylpent-1-ene. It is also possible to polymerize mixtures of these monomers.
The present invention furthermore relates to a process for polymerizing olefins, which comprises carrying out the polymerization in the presence of transition metal complexes of the formulae (Ia), (Iaxe2x80x2) or (Ib) and metallocenium-ion-forming compounds.
Suitable metallocenium-ion-forming compounds are, for example, strong neutral Lewis acids, ionic compounds having Lewis-acidic cations or ionic compounds having Brdnsted acids as cations.
Preferred strong neutral Lewis acids are compounds of the formula (VII)
M4X8X9X10xe2x80x83xe2x80x83(VII)
in which
M4 is an element of the IIIrd main group of the Periodic Table, in particular B, Al or Ga, preferably B,
X8, X9 and X10 are hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, haloalkyl or haloaryl having in each case 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical, or fluorine, chlorine, bromine or iodine, and are in particular haloaryls, preferably pentafluorophenyl.
Particular preference is given to compounds of the formula (VII), in which X8, X9 and X10 are identical, preferably tris(pentafluorophenyl)borane.
Suitable ionic compounds having Lewis-acidic cations are compounds of the formula (VIII)
[(Y1a+)Q1Q2 . . . Qz]d+xe2x80x83xe2x80x83(VIII)
in which
Y1 is an element of the ist to the VIth main group or the Ist to the VIIIth subgroup of the Periodic Table,
Q1 to Qz are radicals carrying one negative charge, such as C1-C28-alkyl, C6-C15-aryl, alkylaryl, arylalkyl, haloalkyl, haloaryl, having in each case 6 to 20 carbon atoms in the aryl and 1 to 28 carbon atoms in the alkyl radical, C3-C10-cycloalkyl, which may be C1-C10-alkyl-substituted, halogen, C1-C28-alkoxy, C6-C15-aryloxy, silyl or mercaptyl groups,
a is an integer from 1 to 6 and
z is an integer from 0 to 5,
d is the difference axe2x88x92z, and is greater than or equal to 1.
Particularly suitable cations are carbonium cations, oxonium cations and sulfonium cations, and also cationic transition metal complexes. The triphenylmethyl cation, the silver cation and the 1,1xe2x80x2-dimethylferrocenyl cation should be mentioned in particular. They preferably have non-coordinating counterions, in particular boron compounds as also mentioned in WO 91/09882, preferably tetrakis(pentafluorophenyl)borate.
Ionic compounds with Brxc3x6nsted acids as cations and preferably likewise non-coordinating counterions are mentioned in Wo 91/09882, and a preferred cation is N,N-dimethylanilinium.
The amount of strong, neutral Lewis acids, of ionic compounds having Lewis-acidic cations or of ionic compounds having Brxc3x6nsted acids used in the process according to the invention as cations is preferably from 0.1 to 10 equivalents, based on the transition metal complex (Ia), (Iaxe2x80x2) or (Ib).
Particularly suitable metallocenium-ion-forming compounds are open-chain or cyclic aluminoxane compounds of the formulae (IX) or (X) 
where R24 is a C1-C4-alkyl group, preferably a methyl or ethyl group, and m is an integer from 5 to 30, preferably from 10 to 25.
These oligomeric aluminoxane compounds are generally prepared by reacting a solution of trialkylaluminum with water, as described, inter alia, in EP-A 284 708 and U.S. Pat. No. 4,794,096.
The oligomeric aluminoxane compounds thus obtained are generally mixtures of both linear and cyclic molecules of different chain length, and m is therefore to be regarded as an average value. The aluminoxane compounds may also be present in a mixture with other metal alkyl compounds, preferably with alkylaluminum compounds.
It has proven advantageous to use amounts of the transition metal complexes (la), (Iaxe2x80x2) or (Ib) and of the oligomeric aluminoxane compounds of the formulae (IX) or (X) which give an atomic ratio of aluminum from the oligomeric aluminoxane compounds to transition metal from the transition metal complexes in the range from 10:1 to 106:1, in particular from 10:1 to 104:1.
It is moreover possible to use, instead of the aluminoxane compounds of the formulae (IX) or (X), aryloxyalumoxanes, as described in U.S. Pat. No. 5,391,793, aminoaluminoxanes, as described in U.S. Pat. No. 5,371,260, aminoaluminoxane hydrochlorides, as described in EP-A 633 264, siloxyaluminoxanes, as described in EP-A 621 279, or mixtures of these, as metallocenium-ion-forming compounds.
In the process according to the invention, preference is given to using both the transition metal complexes (Ia), (Iaxe2x80x2) or (Ib) and the metallocenium-ion-forming compounds in solution, particular preference being given to aromatic hydrocarbons having 6 to 20 carbon atoms, in particular xylenes and toluene.
Suitable for use as a further component are additionally also metal compounds of the formula (XI)
M5(R25)r(R26)s(R27)txe2x80x83xe2x80x83(XI)
in which
M5 is an alkali metal, an alkaline earth metal or a metal of the IIIrd main group of the Periodic Table, i.e. boron, aluminum, gallium, indium or thallium,
R25 is hydrogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl or arylalkyl having in each case 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical,
R26 and R27 are hydrogen, halogen, C1-C10-alkyl, C6-C15-aryl, alkylaryl, arylalkyl or alkoxy having in each case 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbon atoms in the aryl radical,
r is an integer from 1 to 3 and
s and t are integers from 0 to 2, and the total r+s+t corresponds to the valence of M5.
Among the metal compounds of the formula (XI), preference is given to those in which
M5 is lithium, magnesium or aluminum, and
R26 and R27 are C1-C10-alkyl.
Particularly preferred metal compounds of the formula (XI) are n-butyllithium, n-butyl-n-octylmagnesium, n-butyl-n-heptyl magnesium, tri-n-hexylaluminum, triisobutylaluminum, triethylaluminum and trimethylaluminum.
If a metal compound of the formula (XI) is employed, it is preferably present in the catalyst system in an amount which gives the molar ratio of M5 from formula (XI) to transition metal M from formula (Ia), (Iaxe2x80x2) or (Ib) of from 800:1 to 1:1, in particular from 500:1 to 50:1.
In the polymerization process according to the invention, the transition metal complexes (Ia), (Iaxe2x80x2) or (Ib) can also be used on a support material.
The support materials used are preferably finely divided supports which generally have a particle diameter in the range from 1 to 300 xcexcm, in particular from 20 to 90 xcexcm. Examples of suitable support materials are inorganic oxides of silicon, of aluminum, of titanium, or of one of the metals of the Ist or IInd main group of the Periodic Table, or mixtures of these oxides, among which, besides alumina and magnesium oxide and phyllosilicates, preference is in particular given to silica gel.
The carrier may be subjected to a thermal treatment, for example in order to remove adsorbed water, such a treatment generally being carried out at temperatures in the range of from 80 to 200xc2x0 C., preferably of from 100 to 150xc2x0 C., or the support may be calcined. The support may also be treated chemically, in which case customary drying agents, such as metal alkyl compounds, preferably aluminum alkyl compounds, chlorosilanes or SiCl4, are generally employed.
Other suitable supports are finely divided polyolefins, for example finely divided polypropylene.
The process according to the invention may be carried out in the reactors which are usual for polymerizing olefins, either batchwise or preferably continuously. Examples of suitable reactors are continuously-operated stirred tank reactors, agitated powder bed reactors, loop reactors or fluidized-bed reactors, and it is possible, if desired, to use a series of two or more identical or different reactors connected in series. The polymerization reactions may be carried out in the gas phase, in suspension, in liquid and in supercritical monomers, or in inert solvents.
The polymerization conditions are not critical per se. Pressures of from 1 to 3500 bar, preferably from 2 to 100 bar and in particular from 10 to 40 bar have proven suitable, as have temperatures of from 0 to 400xc2x0 C., preferably from 20 to 250xc2x0 C. and in particular from 50 to 100xc2x0 C.
The average molar mass of the polymers may be controlled using the methods which are customary in polymerization technology, for example by introducing regulators such as hydrogen.
Particularly preferably, the transition metal complexes according to the invention can be employed for preparing homo- or copolymers of ethylene or of propylene with other C2-C12-alk-1-enes.
The homo- or copolymers of propylene with other C2-C12-alk-1-enes which homo- or copolymers are obtainable using the transition metal complexes (Ia), (Iaxe2x80x2) or (Ib) are particularly preferably homopolymers of propylene or copolymers of propylene with ethylene and/or but-1-ene. The copolymers of propylene may have a random structure. However, they may also be present in the form of block copolymers or impact copolymers. The homo- or copolymers of propylene are distinguished by a high molar mass and in particular by an isotactic structure of the polymer chains.
The homo- or copolymers of ethylene with other C2-C12-alk-1-enes which homo- or copolymers are obtainable using the transition metal complexes (Ia), (Iaxe2x80x2) or (Ib) are particularly preferably homopolymers of ethylene or copolymers of ethylene with propylene, but-1-ene, hex-1-ene and/or oct-1-ene. The homo- or copolymers of ethylene are distinguished by a very high molar mass. During their preparation, a high rate of comonomer incorporation is observed, owing to which copolymers having a high comonomer content are obtainable, or it is possible to obtain the desired copolymers using a monomer mixture which has a relatively low comonomer content and therefore offers technical advantages in the polymerization.
The homo- or copolymers of ethylene or of propylene with other C2-C12-alk-1-enes which homo- or copolymers are obtainable using the transition metal complexes according to the invention have good technical properties and are suitable for preparing fibers, films or moldings.